Device for introducing cooling water into a conduit for superheated steam



Aug. 18, 1970 B. u. GUSTAFSSON 3,524,592

DEVICE FOR INTRODUCING COOLING WATER INTO A CONDUIT FOR SUPERHEATED STEAM Filed Feb. 27, 1968 Fig.1

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United States Patent Office 3,524,592 Patented Aug. 18, 1970 US. Cl. 239-466 3 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION For obtaining the desired temperature of superheated steam used to drive a steam turbine, for instance, it is known to inject cooling water into the steam conduit by means of adjustable spray nozzles connected to a source of pressurized Water. In the case of greatly varying steam consumption or great variations in the temperature of the steam it is often diificult to obtain a satisfactory admixture with one nozzle only, as the pressure of the water jet becomes too low at a certain degree of throttling. Particularly when operating with high pressure steam it is therefore customary to use a plurality of small nozzles connected to separate high pressure desuperheating water conduits and opened and closed separately in dependence on the amount of water required. However, the relatively narrow water conduits cause a fall of pressure which substantially reduces the injection force. Moreover there is the inconvenience that owing to leakage small quantities of water 'drip through the closed nozzles. This leak water accumulates in the lowest parts of the steam conduit and evaporates only slowly, so that deviations from the desired steam temperature cannot be avoided.

SUMMARY OF THE INVENTION The object of the invention is to provide an easily and exactly controllable device for supplying cooling water into a'conduit for superheated steam, such as a conduit to a steam turbine. The device comprises a cylinder having a conical nozzle at one end. A plurality of passages through the cylinder wall are spaced axially and directed substantially tangertially. At the outside of the cylinder wall these passages communicate with a high pressure desuperheating Water source. A movable piston within the cylinder has a piston rod which projects at the rear end of the cylinder to be connected to an actuating member, and when moved backwards from the orifice this piston is adapted to progressively uncover the outlet ports of the passages. Thus, the supply'of water through the nozzle is increased on rearward movement of the piston and reduced on forward movement thereof. The jets of water entering the cylinder tangentially are caused to rotate rapidly and the water leaves the nozzle in the form of a thin-walled hollow cone which is effectively atomized in the passing flow of steam. In the operation of the device at least the passage next to the nozzle is almost always open, and the rotating water coming from said passage takes then care of any leak water that might be pressed out between the piston and the cylinder wall from the other passages.

In a preferred embodiment of the device, the passages are in direct communication with a relatively large water chamber disposed immediately outside the cylinder wall,

and each passage is designed such that it has a portion with small cross section area next to the inside of the cylinder wall. This eliminates for the greatest part the losses of pressure which have been unavoidable in previous water injection devices, and the water leaves the nozzle at a high velocity and consequently also in rapid rotation.

DESCRIPTION OF THE PREFERRED EMBODIMENT The invention is described in more detail below with reference to the accompanying drawing in which FIG. 1 shows an axial section through a preferred embodiment of the injection device;

FIG. 2 shows a cross section on the line II-II in FIG. 1, and

FIG. 3 shows, on a smaller scale, how the water injection device may be mounted in a steam conduit.

A cylinder 4 (FIG. 1) completely open at one end has at its opposite end an end wall 5 containing a conical nozzle 6 which tapers onto the outside. An annular space 7 is formed between the outside of the cylinder 4 and a surrounding jacket 8 which has one end closed by the end wall 5. The opposite end portion of the jacket 8 projects beyond the cylinder 4 and is closed by an end wall 9. Near the end wall 9 the jacket 8 has an inlet pipe socket 10 adapted to be connected to a high pressure desuperheating water conduit.

An elongated piston 11 within the cylinder 4 has a piston rod 12 which protrudes through a packing box 13 (not shown in detail) inserted in the end wall 9. A pin 14 projecting axially from the inner end of the piston 11 has a conical surface adapted to close the nozzle 6 in the innermost position of the piston.

A plurality of passages 15 through the cylinder wall 4, which are in the form of velocity nozzles are spaced axially as Well as radially, preferably uniformly disposed along an imaginary helical line. As seen in FIG. 2, the passages 15 are directed tangentially to the inner surface of the cylinder 4. In order to reduce the loss of energy, the outer portions of the passages 15 have com paratively large diameter and only next to the inside of the cylinder 4 the passages or velocity nozzles have a more restricted cross section dimensioned with regard to the desired supply of water. In case the cylinder wall is made thin, the enlarged portions of the passages are, of course, unnecessary, but generally a rather thick cylinder is required because of the high pressures used in steam conduits.

In FIG. 3, the device described above is inserted in a curved portion 16 of a steam conduit through a socket 117 welded to the outside of the conduit. A bracket 18 secured to the outer end of the jacket 8 carries a pivot pin 19 for a lever 20 linked to the piston rod 12 at 21. The free end of the lever 20 is adapted to be connected to an actuating member (a servomotor) in a regular sensing the temperature in the steam conduit.

The function of the device has already been indicated above. When the inlet socket 10 of the jacket 8 has been connected to a water service, the passages or velocity nozzles 15 communicate with the source of water over the space 7 between the exterior of the cylinder 4 and the interior of the jacket 8. As soon as the piston 11 has been drawn out so far that the outlet end of the passage 15 located next to the nozzle 6 has been exposed (the position shown in FIG. 1), a jet of Water is injected tangentially into the cylinder 4, where the stream is caused to whirl helically onto and through the nozzle 6. Outside the nozzle 6 the flow of water forms a conical curtain which is effectively atomized by the steam.

Experience shows that the closed velocity nozzles may and sometimes do give a slight leakage which passes between the cylinder 4 and the piston 11 into region adjacent the conical nozzle 6. This leakage is picked up by the jet action of the water leaving the open velocity nozzles 15, which gives this leakage water the necessary swirl as it leaves the concical nozzle 6.

The swirl action is necessary for two reasons, viz:

(1) To obtain a thin water film leaving the conical nozzle so that the flowing steam in conduit 16 can readily atomize and evaporate the water to secure the desired desuperheating.

(2) When the water is accelerated by the velocity nozzles, the flashing of the hot water into steam can cause cavitation and erosion of the plug 14. The swirl, by centrifugal effect causes the water discharged by the tangential velocity nozzles 15 to flow on the inner walls of the cylinder 4 and conical nozzle 6 only. This protects the metal of the plug 14 and the cylinder 4 from erosion caused by imploding steam bubbles. This arrangement also permits the use of very high pressure desuperheating water.

What I claim is:

1. A device for introducing a controlled amount of cooling water into a conduit for superheated steam, comprising a cylinder having a conical nozzle at one end, a plurality of velocity nozzles provided through the cylinder wall to connect the interior of the cylinder to a source of high pressure water located outside of said cylinder, said velocity nozzles being spaced axially and directed substantially tangentially to the cylindrical inner surface of said cylinder, a piston movable in said cylinder to progressively expose said velocity nozzles when moved backwards from a position closing said conical 4 through the rear end of said cylinder connected to an actuating member, the swirling water from said tangential velocity nozzles passing directly through said cylinder and conical nozzle into said steam.

2. A device as claimed in claim 1 wherein the rear cylinder end is in open communication with a jacket adapted to be connected to the source of water and surrounding the cylinder Wall with a clearance, said piston having a rear end surface subjected to the pressure within said jacket, whereby this pressure acts to move said piston in closing direction.

3. A device as claimed in claim 1 wherein each of said velocity nozzles has a relatively wide inlet portion at the outside of said cylinder and a restricted outlet at the inside of said cylinder.

References Cited UNITED STATES PATENTS 1,228,469 6/1917 Mueller 137-625.12

519,083 5/1894 Garrison 239453 X 1,111,244 9/1914 Wilson 137625.12 2,556,308 6/1951 Weatherhead 137625.12 2,692,797 10/1954 Wood et a1. 137625.12 2,921,746 1/ 1960 Burman 239-453 3,219,323 11/1965 Spence 137625.12 X

ROBERT B. REEVES, Primary Examiner H. S. LANE, Assistant Examiner U.S. Cl. X.R. 137-625 1 2 

